![]() ![]() The concept is similar to an old vacuum advance distributor: as the MAP reading drops (vacuum increases), this table will be used to bring in more ignition timing advance. This uses a table similar in appearance to the VE table, where the ECU uses a chart of what timing to run based on RPM and MAP sensor readings. You can also use speed density for ignition timing. This builds a table of values, sometimes called a ‘fuel map’ for short. ![]() It answers the question ‘does this cylinder, at 20% throttle/load and 3000 rpms, fill completely?’ The answer is almost always NO, so the VE table is populated with a number that represents the percentage of how well that cylinder fills with air at atmospheric pressure at each and every load and rpm point. That Volumetric Efficiency table essentially maps out how well the engine fills the combustion chambers at various different loads (think throttle) and engine speeds (RPMs). Using those two components, the ECU ‘looks up’ the amount of fuel needed in the ECUs volumetric efficiency table. There is a MAP sensor (Manifold Air Pressure) which measures the pressure of air entering the engine inside the intake manifold, while the tach (rpm) signal provides the engine’s rpm value. Speed Density Engine Management Systems are fairly common electronic fuel injection systems that rely on two main factors – air pressure and engine speed. Speed Density Systems in the Fox Body Mustang – An Overview 1988 Fox Body Mustang engine bay – with Speed Density System However, this was not the end far from it, it was the beginning of the new age of muscle car performance where adjusting the carburetor was replaced by tuning the mustang and/or programming the ECU. Back in the late 80s, this new Fuel Injection tech was cutting-edge technology, and Ford Mustang fans were initially reluctant, thinking that the era of tinkering with your car was over and that they would not be able to improve their car’s performance. ![]() The only exception was 1988 models bound for California, which had MAF fuel injection a year before due to tighter emissions regulations. This was installed on all V8 models from 1986 to 1988 and then switched to Mass Air Flow design from 1989 onwards known as the A9L EEC-IV ECU. Starting back in 1986, Ford used the Speed Density EEC-IV Engine Management System in the Fox Body Mustang. Gorgeous example of a Four Eyed Fox Body Mustang! First – A little history: 06 MUSTANG GT MASS AIR FLOW SENSOR PROBLEMS HOW TOWanna know how to make the MOST of your engine regardless of whether you’re running Speed Density or Mass Air Flow? Read on and we’ll show you the ways…. And that there is a lot more to it than what those rumors claim. In general, the consensus of the ‘street knowledge’ of the Fox Body Mustang community for years, decades even, was “Speed Density has limitations, and MAF just automatically adjusts no matter what modifications you make to your Mustang so it’s better.”īut is any of that true? Well… let’s just say perspective and control capability is key. And there are other iterations, but generally-these two cover the claims pretty well.If you do so you will have idle surges and cause the car to sometimes shut down.” With Speed Density you can do everything but a Cam change. “With Mass Air the ECU is supposed to accept anything under the sun in the modification world without problems. ![]() 06 MUSTANG GT MASS AIR FLOW SENSOR PROBLEMS MODSbut once mods get heavy (esp cams with diminished vacuum), MAF is more adaptable on its own.” “SD (speed density) is a little faster/more powerful.But I decided to Google/DuckDuckGo them up to see what rumors remain out there in the wild still today. We’ll try to get to the bottom of that here in this article. They knew how to adjust their carburetor, this was all new, and involved computers, scary! And as anything that’s new and scary can do, particularly when it’s not all that well understood just yet, it generated some rumors over the years as to what works, and what doesn’t. Initially feared by enthusiasts as change always takes some getting used to. But then Ford released the first EFI system for its venerable 5.0-liter engine, which completely changed the industry. Until 1986, Mustang fans relied on good old four-barrel carburetors for providing the fueling. There’s probably no single chassis you see more of at the average drag race track, and there is good reason for that! Nearly 30 years after Ford stopped production, the Fox Body Mustang remains insanely popular at the race track. Isn’t Speed Density inferior and MAF the best tuning solution on a Fox Body Mustang? ![]()
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